In the medical field, a capsule endoscope in which an image sensor is stored in a capsule is now used for a diagnosis, in addition to an insertion-type endoscope having the image sensor provided at a distal end of a long insert section.
The capsule endoscope has a hollow capsule body, a dome-shaped transparent cover attached to one end of the capsule body, and an imaging lens that forms an image from light entered through the transparent cover on an image sensor. The capsule endoscope is formed in such a size that the patient can easily swallow (see Patent Documents 1 to 3). Owing to this, the capsule endoscope eliminates burden on a patient occurred in the diagnosis using the insertion-type endoscope, such as swallowing the insert section of the endoscope into his/her mouth or being kept inserting the insert section through the body for long periods of time.